1、Medical electrical equipment Exposure index of digital X-rayimaging systems Part 1: Definitions and requirements for general radiographyBS EN 62494-1:2008raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI British StandardsLicensed Copy: Wang Bin, ISO
2、/EXCHANGE CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSINational forewordThis British Standard is the UK implementation of EN 62494-1:2008. It isidentical to IEC 62494-1:2008.The UK participation in its preparation was entrusted by Technical CommitteeCH/62, Electromedical equipment in
3、 medical practice, to SubcommitteeCH/62/2, Diagnostic imaging equipment.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct appli
4、cation. BSI 2008ISBN 978 0 580 57718 5ICS 11.040.50BRITISH STANDARDBS EN 62494-1:2008Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of the StandardsPolicy and Strategy Committee on 31 March 2009 Amendments issue
5、d since publicationAmd. No. Date Text affectedLicensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSIEUROPEAN STANDARD EN 62494-1 NORME EUROPENNE EUROPISCHE NORM November 2008 CENELEC European Committee for Electrotechnical Standardization Comit Europen de
6、 Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2008 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 62494-1:2008 E ICS 11.040.50 English
7、version Medical electrical equipment - Exposure index of digital X-ray imaging systems - Part 1: Definitions and requirements for general radiography (IEC 62494-1:2008) Appareils lectromdicaux - Indice dexposition des systmes dimagerie numrique rayonnement X - Partie 1: Dfinitions et exigences pour
8、la radiographie gnrale (CEI 62494-1:2008) Medizinische elektrische Gerte - Dosisindikator digitaler Rntgenbildsysteme - Teil 1: Definitionen und Anforderungen fr die allgemeine Radiographie (IEC 62494-1:2008) This European Standard was approved by CENELEC on 2008-10-01. CENELEC members are bound to
9、comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central
10、 Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same statu
11、s as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Pol
12、and, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 62494-1:2008Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSIEN 62494-1:2008 2 Foreword The text of document 62B/680/CDV, future edition 1 of IEC 624
13、94-1, prepared by SC 62B, Diagnostic imaging equipment, of IEC TC 62, Electrical equipment in medical practice, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 62494-1 on 2008-10-01. The following dates were fixed: latest date by which the EN has to be implemented at
14、 national level by publication of an identical national standard or by endorsement (dop) 2009-07-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2011-10-01 In this standard, the following print types are used: requirements, compliance with which can
15、be tested, and definitions: in roman type; explanations, advice, notes, general statements, exceptions and references: in smaller type; TERMS DEFINED IN CLAUSE 3 OF THIS STANDARD, IN EN 60601-1 OR IN IEC/TR 60788, AS REFERENCED IN THE INDEX OF DEFINED TERMS: SMALL CAPITALS. Annex ZA has been added b
16、y CENELEC. _ Endorsement notice The text of the International Standard IEC 62494-1:2008 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following notes have to be added for the standards indicated: IEC 60601-1 NOTE Harmonized as
17、 EN 60601-1:2006 (not modified). IEC 60601-2-43 NOTE Harmonized as EN 60601-2-43:2000 (not modified). IEC 62220-1 NOTE Harmonized as EN 62220-1:2004 (not modified). IEC 62220-1-2 NOTE Harmonized as EN 62220-1-2:2007 (not modified). _ BS EN 62494-1:2008Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STAN
18、DARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSI 3 EN 62494-1:2008 Annex ZA (normative) Normative references to international publications with their corresponding European publications The following referenced documents are indispensable for the application of this document. For dated references
19、 only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Y
20、ear IEC/TR 60788 2004 Medical electrical equipment - Glossary of defined terms - - BS EN 62494-1:2008Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSI 2 62494-1 IEC:2008 CONTENTS FOREWORD.3 INTRODUCTION.5 1 Scope.7 2 Normative references .7 3 Terms a
21、nd definitions .7 4 Requirements .9 4.1 Creation of ORIGINAL DATA9 4.2 Determination of the RELEVANT IMAGE REGION and the VALUE OF INTEREST .9 4.3 Requirements for the EXPOSURE INDEX .10 4.4 Calibration of the EXPOSURE INDEX .10 4.5 Determination of the CALIBRATION FUNCTION .11 4.6 Determination of
22、the INVERSE CALIBRATION FUNCTION 11 4.7 Requirements for the DEVIATION INDEX11 Annex A (informative) Details on the rationale, properties and use of the EXPOSURE INDEX 13 Annex B (informative) Details on the rationale, properties and use of the DEVIATION INDEX 17 Annex C (normative) Beam conditions
23、to be used for calibration18 Bibliography19 Terminology Index of defined terms .20 Figure A.1 Example of an ORIGINAL DATA radiograph with an example of the RELEVANT IMAGE REGION outlined .14 Figure A.2 Histogram of the ORIGINAL DATA for the radiograph shown in Figure A.1 15 Figure A.3 Relative IMAGE
24、 RECEPTOR AIR KERMA required to produce a fixed detector response for the four x-ray beam qualities defined in ISO 9236-1 .16 BS EN 62494-1:2008Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSI62494-1 IEC:2008 3 INTERNATIONAL ELECTROTECHNICAL COMMISS
25、ION _ MEDICAL ELECTRICAL EQUIPMENT EXPOSURE INDEX OF DIGITAL X-RAY IMAGING SYSTEMS Part 1: Definitions and requirements for general radiography FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical com
26、mittees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technic
27、al Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmenta
28、l and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agre
29、ements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees. 3) IEC Publications have the form of recommendations for international use
30、and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promot
31、e international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicat
32、ed in the latter. 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to
33、 IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
34、 expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications. 8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9)
35、 Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62494-1 has been prepared by subcommittee 62B: Diagnostic imaging
36、equipment, of IEC technical committee 62: Electrical equipment in medical practice. The text of this standard is based on the following documents: Enquiry draft Report on voting 62B/680/CDV 62B/703/RVCFull information on the voting for the approval of this standard can be found in the report on voti
37、ng indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. BS EN 62494-1:2008Licensed Copy: Wang Bin, ISO/EXCHANGE CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSI 4 62494-1 IEC:2008 In this standard, the following print types a
38、re used: requirements, compliance with which can be tested, and definitions: in roman type; explanations, advice, notes, general statements, exceptions and references: in smaller type; TERMS DEFINED IN CLAUSE 3 OF THIS STANDARD, IN IEC 60601-1 OR IN IEC 60788, AS REFERENCED IN THE INDEX OF DEFINED T
39、ERMS: SMALL CAPITALS. A list of all parts of the IEC 62494 series, published under the general title Medical electrical equipment Exposure index of digital X-ray imaging systems, can be found on the IEC website. The committee has decided that the contents of this publication will remain unchanged un
40、til the maintenance result date indicated on the IEC web site under “http:/webstore.iec.ch“ in the data related to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. BS EN 62494-1:2008Licensed Copy: Wang Bin, ISO/EXCHANG
41、E CHINA STANDARDS, 08/07/2009 02:40, Uncontrolled Copy, (c) BSI62494-1 IEC:2008 5 INTRODUCTION The direct connection between the level of detector exposure and optical density is well established in film-screen radiology. This is not the case in digital radiography, where almost always a constant im
42、age characteristic is achieved using automatic image processing. Consequently, deviations from the intended exposure, i.e., over- and underexposure, are not noticeable by a corresponding deviation in image brightness. While considerable underexposure results in an increased level of noise, the more
43、alarming aspect (from a radiation protection point of view) is that overexposure cannot be recognized easily in the displayed image. Therefore, various manufacturers of digital radiography systems have introduced so-called exposure indicators for their equipment. These are numbers, determined from t
44、he original image data of each image taken, which allow conclusions about the level of the exposure at the image receptor. However, the exposure indicators are manufacturer or system specific, i.e. they differ for the systems of different manufacturers in their definition and scaling. A unified EXPO
45、SURE INDEX for all digital radiography systems is needed to simplify its usage, e.g. for the establishment of exposure guidelines, particularly when systems of different manufacturers are used within the same department. This standard defines such a concept of the EXPOSURE INDEX. What is laid down h
46、ere refers to the definition, the scale and the general requirements for the EXPOSURE INDEX. The process of its calculation in detail (software algorithm) is excluded from this standard as to not obstruct technical progress. The EXPOSURE INDEX allows the OPERATOR to judge if an image was taken at a
47、detector exposure level suitable for the intended level of image quality. It is important to note that the EXPOSURE INDEX, as defined in this standard, is derived from the image signal, which in turn is usually related to the energy absorbed in the detector, i.e. the detector dose, but not directly
48、to the air kerma at the image receptor. The relation to IMAGE RECEPTOR AIR KERMA (air kerma at the detector surface) is introduced only at one radiation quality through calibration. However, this definition is appropriate as the image quality in digital radiography is determined mainly by the signal
49、to-noise level, which in turn is determined by the absorbed energy. Annex A provides more details on the rationale, properties and use of the EXPOSURE INDEX. The level of detector exposure needed to obtain a suitable level of image quality may vary depending on body part, view, or the x-ray imaging system used, as may the appropriate EXPOSURE INDEX. This standard introduces a second parameter, called DEVIATION INDEX, which quantifies the deviation o
